A light emitting diode (LED) that is a representative light emitting device is a device for emitting a predetermined light through recombination of minority carriers (electrons or holes) as a compound semiconductor having p-n junction structure. The light emitting diode has characteristics of low power consumption, long lifespan, installation in a narrow space, and strong resistance against vibration. In recent years, a white light emitting diode in addition to a single color light emitting diode, e.g. a red, blue or green light emitting diode, has been placed on the market, and its demands have been rapidly increased.
The light emitting diode may implement white light by using a light emitting material which functions as a wavelength converting means. That is, the light emitting material is applied to an upper portion of a light emitting diode, so that a portion of primary light emitted from the light emitting diode and secondary light whose wavelength has been converted by the light emitting material are color-mixed to implement white color. The white light emitting diode configured as described above has been prevalently used since it is lower in price and very simple in principle and structure.
For example, applied to a light emitting diode for emitting blue light is a light emitting material that causes yellowish green or yellow light to be emitted using a portion of the blue light as an excitation source, so that white light can be obtained by color-mixing the blue light emitted from the light emitting diode and the yellowish green or yellow light emitted from the light emitting material.
However, since the light emitting diode has a wide emission angle of a light source and poor straightness, the light emitting diode has currently been used only for short-distance illumination and has a limitation in being used for long-distance illumination and flasher. As such, a light emitting device having strong straightness enough to be used for long-distance illumination and flash has been prevalently required.